1. Determining surface characteristics at candidate MSL landing sites using THEMIS high-resolution orbital thermal inertia data Robin Fergason Philip Christensen MSL Landing Site Selection Workshop May 31, 2006

2. Thermal Inertia Background Used to infer a particle size of the surface layer Helps to identify features, their location and extent on the surface, and their particle size Detect exposed bedrock and dust

3. Exposed Bedrock 800 260 67.6 E Nili Patera 66.9 E 8.7 N 9.5 N Ares Valles Rogers et al., 2005 Christensen et al., 2003a; 2005 950 190 341.6 E341.3 E 5.9 N 6.4 N 3.4 km3.5 km THEMIS-derived thermal inertia overlain onto THEMIS visible

4. Hebes Chasma Interior Layered Deposits V10052001 800 m TI: 190-245 TI: 275-360 TI: 290-420 TI: 125-145 125615 Fergason et al., submitted

5. Thermal Inertia Background I = (ρkc) 1/2 ρ – bulk density k – conductivity c – specific heat Thermal inertia measures a material’s resistance to change in temperature

6. THEMIS-derived thermal inertia Use thermal model developed by H. H. Kieffer –Ls, latitude, local time from spacecraft ephemeris –TES-derived albedo (8ppd) –MOLA-derived elevations (128 epd) –TES-derived dust opacity (2 ppd) every 30° Ls Radiance at 12.57 μm (Band 9) is converted to brightness temperature, correcting for drift and wobble of the spacecraft Interpolate upon a 7-D look-up table

7. THEMIS-derived Thermal Inertia Uncertainties Uncertainties are primarily due to: (1) instrument calibration (2) uncertainties in model input parameters (3) thermal model uncertainties Variations in thermal inertia within a single image are accurate and represent differences in the physical properties of the surface

8. Comparison with TES 25600 180 E 40 S 40 N 180 E 40 S 40 N 180 E THEMIS TES Fergason et al., submitted

9. Comparison of Mini-TES and THEMIS Thermal Inertia Fergason et al., 2006 250430

10. Landing Site Characterization Identify regions of very high or very low thermal inertia –TI > 400 likely has rocky surface [Nowicki, 2006] –TI < 100 is likely dusty and not drivable Evaluate surface properties of the candidate landing sites Predicted surface temperature for the primary mission –Rover design temperature limits: 145 - 310 K –Maximum diurnal temperature range: 145 K

11. Opportunity THEMIS Temperature Mosaic - 2003

12. Opportunity THEMIS Temperature Mosaic - 2006

13. 63.2 E 570175 26.8 N 26.3 N 62.6 E Fergason et al., submitted

14. THEMIS Day and Night IR

16. Predicting Surface Temperature 1.Thermal inertia is derived from THEMIS image 2.The derived thermal inertia value is then used to calculate the surface temperature for a given local time and season Can predict the minimum surface kinetic temperature during the primary mission

17. ASU Will Provide Interpretations of THEMIS and TES thermal inertia data for all candidate landing sites Thermal inertia mosaics of candidate landing site regions (100 m) –Relative thermal inertia values

18. ASU Will Provide Individual thermal inertia images of specific areas of interest (100 m) –Thermal inertia values of specific morphologies Predicted temperature maps of candidate landing site regions (100 m) –Predict range of temperatures –Derive maximum diurnal temperature range